1. Technical Field
This document relates to filters. For example, this document relates to filters that have a gradient of filter pore sizes at different portions of the filters. The filters provided herein can be used in medical applications and non-medical applications.
2. Background Information
Fluid systems are often used in a medical context. Some examples of fluid systems used in the medical context include respiratory systems, anesthesia systems, infusion pump systems, blood transfusion circuits, kidney dialysis systems, extracorporeal membrane oxygenation (ECMO) systems, extracorporeal circuits for heart/lung bypass, and the like.
Some such medical fluid systems include the use of filters. For example, in some cases filters are used to remove undesired elements present in the blood that is flowing through an extracorporeal circuit. Such undesired elements within the blood may include contaminants such as clotted blood components and gaseous bubbles.
Gaseous bubbles within the blood of an extracorporeal circuit presents a concern in relation to patient safety. If gaseous bubbles within blood flowing within an extracorporeal circuit make their way to within the circulatory system of the patient, the gaseous bubbles can become emboli that cause the patient to experience a stroke, for example.
In the context of an extracorporeal blood circuit used during open-heart surgery, for example, gaseous emboli may sometimes be introduced into the circuit at the point of cannulation. That is, if the seal between the venous cannula of the extracorporeal circuit and the patient's anatomy is not essentially airtight, air may pass into, or to even be drawn into, the circuit. When that happens, filters within the extracorporeal circuit play an important role in preventing the gaseous bubbles from being delivered to the patient's vasculature and becoming emboli.